Descriptions

Escape from parasites in their native range is one of many mechanisms that can contribute to the success of an invasive
species. Gnathiid isopods are blood-feeding ectoparasites that infest a wide range of fish hosts, mostly in coral reef habitats.
They are ecologically similar to terrestrial ticks, with the ability to transmit blood-borne parasites and cause damage or even
death to heavily infected hosts. Therefore, being highly resistant or highly susceptible to gnathiids can have significant
fitness consequences for reef-associated fishes. Indo-Pacific red lionfish (Pterois volitans) have invaded coastal habitats of the
western tropical and subtropical Atlantic and Caribbean regions. We assessed the susceptibility of red lionfish to parasitic
gnathiid isopods in both their native Pacific and introduced Atlantic ranges via experimental field studies during which
lionfish and other, ecologically-similar reef fishes were caged and exposed to gnathiid infestation on shallow coral reefs.
Lionfish in both ranges had very few gnathiids when compared with other species, suggesting that lionfish are not highly
susceptible to infestation by generalist ectoparasitic gnathiids. While this pattern implies that release from gnathiid
infestation is unlikely to contribute to the success of lionfish as invaders, it does suggest that in environments with high
gnathiid densities, lionfish may have an advantage over species that are more susceptible to gnathiids. Also, because
lionfish are not completely resistant to gnathiids, our results suggest that lionfish could possibly have transported blood
parasites between their native Pacific and invaded Atlantic ranges.